PARIS — Federal agents raided a northeast Texas manufacturing plant Tuesday and detained about 160 alleged undocumented immigrant workers as part of an ongoing criminal investigation into a company that makes vehicle trailers.

Immigration and Customs Enforcement's Homeland Security Investigations office in Dallas said the operation was thought to be one of the largest of its kind nationally in a decade.

The raid was part of a criminal investigation into the Sumner-based company Load Trail for illegally employing foreign workers — a rare enforcement move reserved for repeat violators.

Katrina Berger, special agent in charge of ICE's Homeland Security Investigations office in Dallas, said at a Tuesday afternoon news conference that while the primary focus was the criminal investigation, "We can't turn a blind eye to those illegal workers."

Berger said the message for other employers who engage in illegal hiring is: "We're watching. And we're coming."

Sumner is an unincorporated community of fewer than 100 residents about 100 miles northeast of downtown Dallas and 12 miles west of Paris.

Load Trail representatives couldn't be reached for comment.

Load Trail began as a family-owned business in 1996 and has grown to employ more than 500 people on its 100-acre site, according to the company's website.

The company paid a $445,000 fine in 2014 for hiring undocumented immigrants to work in its plant, according to an ICE report. "The company employed more than 179 unauthorized workers" at the time, the report said.

Dennis Perry, a $16-an-hour Load Trail factory worker, said armed agents came in from "every corner" right after his break in the first shift. "They just came and raided from every entrance there was."

Then, he said, "they drew their guns and told everyone to hit the ground."

Some workers went running. They were tackled, Perry said. A few workers hid by shelves but were quickly discovered. All were searched for weapons and drugs, Perry said.

As part of a criminal search warrant, agents questioned employees and seized employment documents. Berger said agents were told that many of the alleged undocumented workers were using fraudulent identification documents.

Many workers were "administratively arrested" and processed for immigration violations. Berger said no criminal arrests were made Tuesday.

Suspected undocumented immigrants, mostly men, were issued notices to appear in immigration court for civil proceedings. Many were expected to be released until those hearings.

The company's owners face the possibility of criminal indictment.

In the past, employers deemed "abusive and exploitative" have been charged by ICE with alien smuggling, alien harboring, document fraud, money laundering and conspiracy.

Berger said such illegal hiring practices give companies an unfair advantage, subject workers to low wages and potentially dangerous conditions, and take jobs away from U.S. citizens.

More than 300 federal agents and support staffers, including translators, were part of Tuesday's operation, which included Air and Marine Operations, an agency within U.S. Customs and Border Protection. Local law enforcement officials were not asked to participate.

One year ago, ICE's acting director at the time, Thomas Homan, told The Dallas Morning News that the immigration crackdown supported by President Donald Trump would make employers its next target.

"You are going to see a lot more worksite enforcement this year," Homan said. "We will take action against those employers who knowingly hire illegal aliens."